Safety stop mechanism



April 10, 1962 M. R. BOWERMAN SAFETY STOP MECHANISM 2 Sheets-Sheet 1Filed April 21, 1958 INVENTOR Myron R. Bowermcn April 10, 1962 FiledApril 21, 1958 Fig.3.

M. R. BOWERMAN 3,02

SAFETY STOP MECHANISM 2 Sheets-Sheet 2 INVENTOR Myron R. Bowermon M 4%"W W tion.

United States Patent Ofiice 3,028,977 Patented Apr. 10, 1962 3,028,977SAFETY STOP MECHANISM Myron R. Bowerman, Washington Township, StarkCounty, Ohio, assignor to The Alliance Machine Co., Alliance, Ohio, acorporation of Ohio Filed Apr. 21, 1958, Ser. No. 729,816 Claims. (Cl.212-21) This invention relates to safety stop mechanisms andparticularly to safety stop mechanisms for overhead cranes and the like.

There are times, during the operation of a crane, when the crane blockwill accidentally be brought up against the crane frame with such forcethat one or more cable reevings will be broken. When this occurs, thecrane block will fall to the floor, often causing physical damage toplant and equipment and injury to men on the working floor. Varioustypes of controls have been tried in an effort to provide some means forstopping the drive motors. These have not been entirely satisfactory forvarious reasons but primarily because the considerable amounts of rotarymomentum in the motors, drives and cable drums are sufficient to carrythe block with sufficient force to break the cables at unpredictabletimes. Various spring means have been proposed for mounting on the craneblock, but these have generally been objectionable because of theirbulkiness and added weight on the crane block.

I have invented a safety stop mechanism which overcomes the deficienciesof the heretofore proposed safety means. My invention will absorb thevery considerable amounts of stored kinetic energy which are presentwhen a crane block is raised without stopping against the crane frame.

In a preferred embodiment, I provide a crane mechanism comprising aframe, a lifting block depending from said frame on hoisting cables,means on the frame for raising and lowering the lifting block on saidcables, and resilient means on the frame in the path of travel of thelifting block adapted to be contacted by the lifting block beforereaching the frame and to exert increasing force against the movingblock. Preferably, the resilient means are spaced bell cranks pivoted onthe frame with one end in the path of the lifting block and compressiblemeans acted on by the opposite end of the bell crank to be compressedwith increasing resistance as the bell cranks are rotated.

In the foregoing general description, I have set out certain objects,advantages and purposes of the inven- Other objects, advantages andpurposes of this invention will be apparent from the followingdescription and the accompanying drawings in which:

FIGURE 1 is a side elevation of a preferred embodiment of my invention;

FIGURE 2 is an end elevation of the preferred embodiment of my inventionshown in FIGURE 1;

FIGURE 3 is a view on the line III-III of FIGURE 2 partly in section;

FIGURE 4 is a section on the line lV-IV of FIGURE 3; and

FIGURE 5 is a section on the line V--V of FIGURE 3.

Referring to the drawings, I have illustrated a crane trolley having aframe provided with wheels 11 of conventional design. A hook block 12carrying a lifting hook 13 is suspended on hoisting cables 14 from ahoist drum 15 Bell cranks 16 and 17 are journaled on pins 18 on alifting beam 19 extending transversely of the frame 10. The bell cranks16 and 17 are made up of spaced members, one on each side of the web1921 of beam 19. One end 16a and 17a, respectively, of each member ofeach pair of bell crank members 16 and 17 extends below the lifting beam19 in the path of the hook block 12 and are connected by a pin 20. Aroller contact 21 is journaled on each of pins 20 to contact a cap 22 onthe hook block 12. The other ends 16b and 17b of the paired members 16and 17 lie beside the web 19a on opposite sides thereof. Parallel rowsof Bellville spring washers 23 are mounted on spaced shafts 24 extendingparallel to each side of the web 19a of the lift beam 19-. End plates 25and 26 are slidably fitted on the ends of shafts 24 and bear against theBellville springs. A hollow shaft 27 is fixed at one end to end member25. The other end of shaft 27 is attached to a yoke 28 which passesaround end member 26 and is fixed on a pin 29 through the end 17b ofbell crank 17. A shaft30 is fixed at one end to end member 26 andextends through the hollow interior of shaft 27. The opposite end ofshaft 30 is pivoted on a pin 31 in the end 1612 of bell crank 16.

The safety mechanism of this invention operates as follows: When thehook block 12 is raised by the hoist drum 15, the cap strikes therollers 21 on the ends of the two bell cranks 16 and 17. If theconventional limit switch (not shown) fails to function, the bell crankscontinue to raise. This causes bell crank 16 to draw rod 30 towards theleft viewing FIGURE 2 and bell crank 17 to draw shaft 27 to the rightviewing FIGURE 2, thereby drawing the end members 25 and 26 toward eachother. This causes the Bellville springs 23 to be compressed and togradually exert an increased resistance to the raising of the hookblock, thereby absorbing the kinetic energy of the block so as togradually bring the block to a stop. This gradual reduction in the speedof the block will bring it to a stop without breaking the liftingcables, whereas, if the block were brought against the lifting beamwithout this reduction in speed and energy, the lifting cables would inall likelihood snap.

While I have illustrated and described a present pre ferred embodimentof my invention, it will be understood that this invention will beotherwise embodied within the scope of the following claims.

I claim:

1. A hoisting mechanism comprising a frame, hoisting cables dependingfrom said frame, a lifting block depending from said frame on saidhoisting cables, means on the frame for raising and lowering the liftingblock on said cables, a pair of bell crank means pivoted on the frame onopposite sides of the path of lift block travel having one end dependingbelow the frame in the path of travel of the lifting block when raisedand lowered, resilient means on the frame extending transversely of thedirection of lift block travel of such size as to be capable ofabsorbing the kinetic energy of the moving lifting block and the raisingand lowering means, connections from the other end of said bell crankmeans engaging the resilient means whereby increasing force is exertedon the bell crank and in turn on the lifting block as the block israised in contact with said one end of the bell crank and striker meanson the lifting block adapted to engage both bell crank means when theblock is raised.

2. A hoisting mechanism comprising a frame, hoisting ropes dependingfrom said frame, a lifting block depending from said frame on saidhoisting ropes, means on the frame for raising and lowering the liftingblock on said ropes, spaced pairs of bell crank means pivoted on theframe two on each side of the path of travel of the lifting block, eachhaving one end directed toward the other and depending below the framein the path of travel of the lifting block when raised and lowered,resilient means on the frame extending transversely of the direction oflift block travel of such size as to be capable of absorbing the kineticenergy of the moving lifting block and the raising and lowering means,between the other ends of said bell cranks, connections between the saidother ends and the resilient means whereby increasing resistance tomovement is exerted on the bell cranks as the lifting block is raised incontact with said one end of the bell cranks and striker means on thelifting block adapted to engage both bell crank means when the block israised,

3. A hoisting mechanism comprsing a frame, hoisting ropes depending fromsaid frame, a lifting block depending from said frame on said hoistingropes, means on the frame for raising and lowering the lifting block onsaid ropes, a pair of spaced bell crank means pivoted intermediate theirends on the frame on opposite sides of the path of lift block travel,each having one end depending below the frame in the path of travel ofthe lifting block when raised and lowered, said one ends being directedtoward each other, horizontally extending spring means on the frame ofsuch size as to be capable of absorbing the kinetic energy of the movinglift block and the raising and lowering means, between the other ends ofsaid bell cranks, connections between the said other ends and the springmeans acting to compress the spring means when said one ends are movedtoward the frame by the raising of the lifting block whereby increasingresistance to movement is exerted on the bell cranks as the liftingblock is raised in contact with said one end of the bell cranks andstriker means on the lifting block adapted to engage both bell crankmeans when the block is raised.

4. A hoisting mechanism comprising a frame, hoisting ropes dependingfrom said frame, a lifting block depending from said frame on saidhoisting ropes, means on the frame for raising and lowering the liftingblock on said ropes, a lifting beam on the frame beneath the raising andlowering means, spaced paired bell crank means pivoted intermediatetheir ends on the lifting beam two on each side of the path of liftblock travel, each having one end depending below the beam in the pathof travel of the lifting block when raised and lowered, said end of eachpair connected by a shaft carrying a roller, a pair of spaced parallelrods extending generally between the other ends of said bell cranks oneach side of the lifting beam parallel to the length of the beam,comprcssible spring means on said rods of such size as to be capable ofabsorbing the kinetic energy of the moving lifting block and the raisingand lowering means, means slidable on the rods connected to said otherends of said bell cranks acting to compress the spring means when saidone ends are moved toward the lifting beam by the raising of the liftingblock whereby increasing resistance to movement is exerted on the bellcranks as the lifting block is raised in contact with said one end ofthe bell cranks and striker means on the lifting block adapted to engageboth bell crank means when the block is lifted.

5. A hoisting mechanism as claimed in claim 4 wherein the spring meansare Bellville spring washers slidable on the parallel rods.

References Cited in the file of this patent UNITED STATES PATENTS1,848,932 Brinley Mar. 8, 1932 1,867,450 Genzmer July 12, 1932 1,951,088Feeley et al Mar. 13, 1934 1,975,094 Fitch Oct. 2, 1934 2,128,660Moorhouse Aug. 30, 1938 2,260,634 Mullner Oct. 28, 1941 2,336,485 KnoxDec. 14, 1943 2,708,110 Clay May 10, 1955 2,778,506 Harry Jan. 22, 19572,844,431 Harnlett July 22, 1958 2,845,263 Gund July 29, 1958

